The present invention relates to a storage subsystem in an information processing system, and in particular, to a storage subsystem including a plurality of interfaces conforming to a plurality of data formats.
Recently, there has been intensively achieved xe2x80x9cdownsizingxe2x80x9d of computer systems in which jobs conventionally conducted by a mainframe are carried out by small-sized computers such as personal computers and workstations. In the mainframe, there has been accumulated a large amount of information through jobs conducted in the past. In this situation, it is desired that the information accumulated in the mainframe is accessed from small-sized computers. Heretofore, there has been known a technology in relation to file sharing or file conversion between different operating systems in which, for example, an operating system of a workstation accesses a file of a file system created by an operating system of a personal computer. For some of the personal computer file systems, information such as file formats and positions of file management information are generally opened. Therefore, the workstation operating system can interpret a file format of a personal computer in the workstation to access a file in a file system created by the personal computer operating system.
In the mainframe, a disk access is conventionally accomplished in the count-key-data (to be abbreviated as CKD herebelow) format; whereas, a fixed length data (to be abbreviated as FBA format herebelow) format is used for the disk access in the open system. Consequently, to share a file between the main and open systems, it is required to absorb the difference between the data formats. JP-A-9-258908 (corresponding to U.S. patent application Ser. No. 08/774,447) describes a technology to absorb the data format discrepancy. That is, there is provided a storage having a function in which when the open system reads a record written in the CKD format in the storage, the data is presented as data in a fixed length format, namely, the data is shaped in a particular format. Additionally, on the open system side, there is disposed means to interpret the fixed length data thus shaped in the particular format to thereby obtain a data field therefrom. With this provision, it is possible for the open system to read a data set written in the storage by the mainframe.
Although JP-A-9-258908 (corresponding to U.S. patent application Ser. No. 08/774,447) describes a method for the open system to read a data set from the mainframe, no description has been given of a method of writing data in a file system of the mainframe. On the open system side, there exists neither a concept of the count field of the CKD data nor a concept for the cylinder and the head described therein. Therefore, for the open system side to write the CKD data, there is required means to create a count field on the open system side. Moreover, for the mainframe side to read a data set written on the open system side, it is necessary to update, for example, management system of the file system generated on the mainframe side.
It is therefore an object of the present invention to provide an interface conforming to the CKD format and an interface conforming to the FBA format in a disk device so that the open system writes data in the file system of the mainframe.
In order to achieve the object above, there is provided a computer system in accordance with the present invention. The computer system in accordance with the present invention includes a first computer, a second computer, and a storage subsystem having a plurality of interfaces to establish connections to the first and second computers. The first computer accesses the storage subsystem in accordance with a count-key-data format and the second computer accesses the storage subsystem in accordance with a fixed length block format. The second computer includes access means for accessing a record in the count-key-data format, which is written by the first computer in the storage subsystem, via an interface conforming to a fixed length block format, acquiring means for acquiring only user data from the record read by the accessing means, and interpreting and using means for interpreting and utilizing management information of a file system and the like written in a record generated in the storage subsystem by the first computer. In addition, the second computer includes writing means for converting write data into a record in the count-key-data format and writing the record in the storage subsystem via an interface conforming to a fixed length block format.
Furthermore, in the data writing operation, the writing means of the second computer refers to management information of a file produced by the first computer in the storage subsystem, interprets a data format of the file, and writes therein records conforming to a data format of the file. Furthermore, by rewriting the management information of the file at completion of the writing operation of the second computer, it is possible for the first computer to read the record written by the second computer.
Moreover, the storage subsystem of the computer system in accordance with the present invention has a one-to-one correspondence between an address specified by a cylinder number and a head number in the count-key-data format and an address specified by a logical block number in the fixed length block format. The writing means of the second computer handles requested data as a record in the count-key-data format, generates a count field of a record in the count-key-data format in accordance with an address of a write position to thereby obtain through conversion a record in the count-key-data format, and calculates a logical block number in a fixed length format in association with a cylinder number and a head number for a writing operation in the storage subsystem so as to access the storage subsystem in accordance with the logical block number.
Additionally, in accordance with the present invention, the storage subsystem of the computer system includes a storage to store data in the fixed length block format, and the first computer includes writing means which converts a record written by the first computer via the count-key-data interface in a file into a sequence of data in the fixed length block format in a predetermined format to thereby write the sequence of data in the storage. Moreover, the writing means of the second computer includes means similar to means of the storage subsystem to convert a record into a sequence of data in the fixed length block format such that the converted sequence of data in the fixed length block format is written in the storage subsystem via an interface conforming to the fixed length block format.
Furthermore, the writing means divides the record in the counter-key-data format into fixed-length blocks for the writing thereof. When last one of the divided records has a length less than the fixed length, a predetermined sequence of data is added thereto beginning at the end of data to resultantly obtain a fixed length block so as to write the block in the storage subsystem.